1) Field of the Invention
The present invention relates to a ceramic structure, and particularly relates to a ceramic structure which is suitably used for fashion accessories, such as rings, pins; ornaments, such as wall hangers; glass products, such as glassware; or ornaments applied to the surface of artificial teeth.
2) Related Art
Ornamental products using gold or platinum materials, gold or platinum plates where a metal curving technique is applied, or glass plate on the surface of which ornamentally designed gold or platinum foil is attached, or ornaments where a designed gold or platinum foil is sandwiched between transparent glass plates are well known.
However, a large amount of gold or platinum is necessary to obtain the ornamental products made of gold or platinum material on which a metal curving technique is applied, so the cost for manufacturing the products becomes high. Further, these metal materials are comparatively soft so that the portions where the ornamental design is applied is apt to be deformed and the surface of these products is apt to crack.
Other ornamental products on which designed gold or platinum foil is fused and attached have problems in their durability because the foil peels when the products are used for a long time. Further, other products where a gold or platinum foil is sandwiched between transparent glass plates have the inconvenience of being thick and heavy.
Concerning ornaments applied on the surface of artificial teeth, many efforts are being paid to realize shape and color close to a natural tooth, however, ornamental designs on the surface of artificial teeth have not been yet.
In order to solve the problems of conventional techniques, the present inventor suggests a ceramic structure having two layers, i.e. a basic layer and a second layer where an ornamental designed gold foil is held between the layers in Japanese Patent Application No. 95-70329 and 95-264602. However, the generally used ceramic material requires a high temperature about 1300xc2x0 C. to be burnt, and therefore, a glaze layer (the second layer) peels off from a basic layer or many cracks are caused in the glaze layer due to the difference in the coefficients of thermal expansion between the basic layer and the glaze layer (second layer). As a result, the gold foil or platinum foil sandwiched between the basic layer and the glaze layer is deformed.
The present invention has for its object to provide a thin and light ceramic structure having a plurality of layers between which an ornamental designed foil made of gold or platinum is arranged. According to the invention the brightness and the design of the foil made of gold or platinum can be kept as is for a long period without having any damage.
The present invention has another object to provide an artificial tooth on which an ornamental design is applied by using the ceramic structure according to the invention.
In order to solve the tasks, a ceramic structure according to the present invention comprises a first layer composed of a ceramic material which is fused at a medium temperature, a second layer composed of a ceramic material which is fused at a low temperature and/or a glaze material, and a gold and/or platinum material having a high purity being sealed between said first and second layers.
In this specification, the ceramic material fused at a medium temperature means a ceramic material which is burnt at a temperature of 920 to 960xc2x0 C., more preferably about 940xc2x0 C.; and the ceramic material fused at a low temperature means a ceramic material which is burnt at a temperature of 660 to 810xc2x0 C., more preferably about 720 to 780xc2x0 C. If the burning temperature of the second layer is higher than that of the first layer, the first ceramic layer, which works as a basic layer, is shrunk and then deformed, so that it becomes difficult to form the final products in a good manner. Then, in the first invention of the present application, a ceramic material which is fused at a medium temperature is used as a first layer and a ceramic material which is fused at a low temperature and/or a glaze material is used as a second layer, so that the temperature for burning the second layer (2nd burning) does not become higher than the temperature for burning the first layer (first burning) in order to prevent the deformation of the first layer. According to the present invention, the difference between the temperature at the first burning for the first layer and the temperature at the second burning for the layer becomes about 150 to 200xc2x0 C. Therefore, the deformation of the first layer after burning the second layer could be completely prevented.
Further, it is preferred to use a ceramic material fused at a medium temperature used for the first layer, whose coefficient of thermal expansion is 102 to 152 (xc3x9710xe2x88x927/xc2x0 C.). It should be noted that the structure according to the first invention can preferably be used to apply an ornamental design on the surface of the artificial tooth, where an accurate technique is required to manufacture it.
In the case that a ceramic material fused at a low temperature is used for the second layer, it is desired to burn the structure under a reduced pressure. Because air bubbles included inside of the ceramic material fused at a low temperature are removed by burning under reduced pressure, and thus the transparency of the second layer becomes better. The burning under a reduced pressure is conducted in a furnace having a degree of vacuum of about 720 to 760 mmHg. Further, it is desired that the gold or platinum used as a material for the ornamental designed foil has a purity of 98% or more, and includes 1% or less silver.
It may be possible to use only a glaze material, or a mixture of glaze material and a ceramic material fused at a lower temperature for the second layer. If the amount of glaze material is great, the fluid characteristic thereof becomes better and the surface of the final product then becomes smooth.
A ceramic structure according to the second invention comprises a first layer composed of a glass material or a glass substance, a second layer composed of a glaze material and/or a fritting glass material, and a gold and/or platinum material having a high purity being sealed between said first and second layers.
The conditions for fusing the glass material as the first (basic) layer and the glaze material or the fritting glass material as the second layer are:
(1) The coefficients of thermal expansion of both materials of the first and second layers are close together;
(2) The softening temperature of the glass material of the basic layer is matched to the melting temperature of the glaze material or the fritting glass of the second layer; and
(3) Even if the glaze material or the fritting glass of the second layer is fully fused, the glass material of the basic layer is not fused.
Therefore, the glass material for the basic layer withstands burning at a temperature of 500-820xc2x0 C. at which the glaze material or the fritting glass material of the second layer is completely fused; and the material should preferably have the coefficient of thermal expansion of 80 to 140 (xc3x9710xe2x88x927/xc2x0 C.) where the measurement is conducted at a temperature of 25 to 450xc2x0 C. Crystal glass, fusing glass or optical glass can suitably be used for the material of the basic layer of the ceramic structure according to the second invention. It should be noted that daily used glass products, such as eye glasses, or glassware can be used as the basic layer. Further, bowls or ornamental objects on which cloisonne are applied can preferably be used as the basic layer made of glass substance.
By using such a thermostable glass material for the basic layer, it can be prevented that the basic layer is deformed when the second burning is conducted to form the second layer made of the glaze material or fritting glass material. Therefore, according to the second invention, it becomes possible to enclose the ornamental designed foil made of gold or platinum on the surface of the basic layer which has a large surface. Further, when the coefficient of the thermal expansion of the second layer, i.e. the glaze material or the fritting glass material as the second layer is almost the same as the above mentioned coefficient of the thermal expansion of the basic layer, no crack is caused on the surface of the final products.
When the ornament is applied on the surface of glass products, such as glassware or eye glasses, it might be possible to conduct the second burning in a condition that only the portion where the gold or platinum foil is temporarily adhered is covered by the glaze material or the ceramic material fused at a low temperature.
The method for manufacturing the ceramic structure according to the first invention of the present application, has the following steps:
burning a ceramic material fused at medium temperature at a temperature of 920 to 960xc2x0 C., preferably 940xc2x0 C. to obtain a first layer (a basic layer)
arranging a foil made of gold and/or platinum on said first layer with a binding agent and heat it up until the temperature in a furnace becomes 750xc2x0 C. to temporarily adhere said foil on the first layer;
applying a ceramic material fused at a low temperature and/or a glazing material on the surface of said first layer so as to cover at least an area where said foil is applied to obtain a second layer; and
burning a structure having said first and second layers and said foil until the temperature in a furnace becomes at 760 to 810xc2x0 C., more preferably at 780xc2x0 C.
Furthermore, the method for manufacturing the ceramic structure according to the second invention of the present application, has the following steps:
preparing a first layer made of glass material or glass substance;
arranging a foil made of gold and/or platinum with a binding agent and heat it up until the temperature in a furnace becomes 720 to 780xc2x0 C., more preferably 750xc2x0 C. to temporarily adhere said foil on the first layer;
applying a ceramic material fused at a low temperature and/or a glazing material on the surface of said first layer so as to cover at least an area where said foil is applied to obtain a second layer; and
burning a structure having said first and second layers and said foil until the temperature in a furnace becomes 760 to 820xc2x0 C., more preferably 780xc2x0 C.
Further, the ceramic structure according to the first invention of the present application can suitably be applied to accessories for artificial teeth. In this case, it is desired to use only a glaze material for dental use or a mixture of the glaze powder for dental use and a glazing material which includes no or only a little amount of Pb is used as the material for the second layer in order not to have a bad effect on the body.